If this is for your studies, you can always look if there's a cheap copy available second hand from another student.
I kinda want an free PDF of the textbook
Free things are always nice, but unfortunately it seems as if this book isn't too popular, so it might not be easy to find a PDF copy floating around somewhere. I personally don't like digital textbooks and feel I don't learn as well from them, so I much prefer the dead tree format.
I should add, have you checked your local library?